The present invention relates to a medical energy irradiating apparatus for irradiating a living tissue with energy to treat or diagnose the living tissue. More particularly, the present invention relates to a medical energy irradiating apparatus including a temperature sensor disposed in an insert portion to be inserted into a living body for accurately measuring the temperature of the living body, which it is being irradiated with an energy during treatment or diagnosis, without the need for thrusting into the living body.
There have been known in the art medical energy irradiating apparatus having an elongate insert portion to be inserted into a living body through a body cavity or a small incision. When the insert portion is inserted into the living body, the insert portion irradiates a living tissue including an affected region with an energy such as a laser beam, a microwave, a radio wave, an ultrasonic wave, or the like to thermally modify, necrose, coagulate, cauterize, or evaporate the tissue of the affected region or a surrounding tissue including the affected region.
The medical energy irradiating apparatus generally directly apply the energy to the surface layer of a living tissue or the affected region positioned closely thereto. The medical energy irradiating apparatus are also used to treat, with heat, an affected region positioned deeply in a living tissue, such as a prostatic hypertrophy, a prostatic cancer, or a prostatitis.
For example, International Publication No. WO93/04727 discloses a technique proposing a process of applying a laser beam to solidify or contract some tissue of a cancer or a prostate. According to this technique, a coolant is introduced into a balloon to prevent the surface of a urethra held in contact with the balloon from being heated, while only the cancer or the prostate located inside is being heated. However, since the laser beam is applied from a fixed laser beam irradiator, the laser beam needs to be applied at a low output level to prevent the surface of a urethra from being heated. Hence, the laser beam needs to be applied for a long period of time. International Publication No. WO93/04727 reveals a balloon catheter having a thermocouple disposed in the balloon to be located in an intermediate position in a prostatic urethra for monitoring the temperature of a urethral tissue. The thermocouple is disposed within the balloon and held out of direct contact with the urethra, and the coolant is circulated through the balloon. Therefore, the temperature measured by the thermocouple does not appear to be accurately representative of the temperature of the prostatic urethra. U.S. Pat. No. 5,964,791 discloses a process of thrusting into a prostate with a temperature sensor to accurately measure the temperature of the urethra (direct measuring process).
U.S. Pat. No. US6,579,286 discloses, as an example of heat treatment device, a laser beam irradiating apparatus for guiding a laser beam into a urethra to treat a prostatic hypertrophy. The laser beam irradiating apparatus has a laser beam irradiation portion that is continuously movable to change the direction of the applied laser beam at all times. However, since the laser beam irradiating apparatus is arranged to concentrate the laser beam on a target region, the target region is heated to a high temperature while holding a surrounding tissue around the target region at a lower temperature. Even if the target region is positioned deeply in the living tissue, therefore, any damage to the living tissue that is located between the laser beam irradiator and the target region is minimized.
A therapeutic procedure for treating a prostatic hypertrophy with the laser beam irradiating apparatus will be described below. First, the doctor inserts the insert portion of the laser beam irradiating apparatus into the urethra of the patient. The insert houses therein a laser beam irradiator having a reflecting surface for reflecting a laser beam which is generated by a laser beam generator, guided by an optical fiber, and emitted from the tip end of the optical fiber. The insert portion also houses therein an endoscope, and inlet outlet pipes for a coolant for cooling the laser beam irradiator. Then, the doctor positions the laser beam irradiator while observing the urethra with the endoscope in the insert through an observation window disposed in the insert, and then applies the laser beam to a target region in the patient.
The heat treatment device referred to above needs to measure the temperature of a treated region in order to monitor the treatment in progress. The temperature of the treated region (the target region to be irradiated with the laser beam) positioned deeply in the living body can be measured by a process of thrusting into the living tissue with a temperature sensor to directly measure the temperature of the deep region (direct measuring process) or a process of bringing a temperature sensor into contact with the surface layer of the living body near the treated region to accurately measure the temperature of the surface layer of the living body and estimating the temperature of the deep region based on the measured temperature.
Though the direct measuring process is able to accurately measure the temperature of the treated region, it is disadvantageous in that it invites side effects such as hemorrhage and infectious disease because the living body is injured by being pierced with the temperature sensor, resulting in an increased number of days that the patient needs to stay in the hospital. For this reason, there has been a demand for a technique to accurately measure the temperature of the surface of the living body while it is being treated by an energy irradiation, thereby increasing the accuracy to estimate the temperature of a deep living tissue.
Problems that arise regarding the accurate measurement of the temperature of the surface of the living body will be described below. Conventional Temperature sensors have a temperature measuring element such as a thermistor and two leads connected thereto, which are placed in a tangle-free manner in a protective tube. However, the protective tube makes the insert portion to be inserted into the living body thick, posing an increased burden on the patient. The leads that are employed tend to cause the thermistor to be installed in different positions, making it impossible to measure accurate temperatures.
It may be proposed to place the temperature measuring element and the leads within the insert portion. If the temperature measuring element is placed in the insert portion of an energy treatment device where a coolant is circulated in the insert portion for cooling an energy emission unit and the living body contacted by the insert portion, then the coolant affects the temperature measuring element. Consequently, there has been desired a temperature sensor less susceptible to the coolant and is yet capable of accurately measuring the surface temperature of a living body.
One solution would be to attach the temperature measuring element and the leads to the outer surface of the insert. However, this approach needs to meet the following requirements:
1. The temperature measuring element will not be affected by the coolant.
2. The temperature measuring element will be installed easily and accurately in a desired position.
3. When the temperature measuring element and the leads are attached, the leads will not be damaged and will keep electrically connected to the temperature measuring element.
4. The insert portion will not have protrusions on its surface, which would otherwise be liable to damage the living body when the insert portion is inserted into the living body.
5. The temperature measuring element will not be directly affected by the energy that is applied to the living body.